Discovery of Sulfur-Containing Compounds in Broccoli with GC-TOFMS

Significance of the Topic

Understanding volatile and semi-volatile sulfur compounds in broccoli is essential because they drive aroma, flavor, and nutritional attributes. Processing steps such as freezing can transform glucosinolate derivatives into isothiocyanates, altering sensory profiles and potential health benefits.

Objectives and Study Overview

The study aims to differentiate raw broccoli from processed frozen broccoli through non-targeted volatile profiling. By focusing on sulfur-containing analytes, the investigation seeks markers that reveal chemical changes induced by processing.

Methodology and Instrumentation

Broccoli samples (2.5 g each) were incubated at 50 °C for 5 minutes and extracted via HS-SPME using a DVB/Car/PDMS fiber for 30 minutes. Analysis was performed on an Agilent 7890 GC with LECO L-PAL3 autosampler, Rxi-5ms column (30 m × 0.25 mm × 0.25 μm), He carrier gas (1.0 mL/min), and a LECO Pegasus BT TOFMS (mass range 35–650 m/z, acquisition rate 10 spectra/s).

Instrumentation Used

• GC-TOFMS: LECO Pegasus BT
• Autosampler: LECO L-PAL3 on Agilent 7890
• SPME Fiber: DVB/Car/PDMS

Results and Discussion

Deconvolution of the total ion chromatogram revealed hundreds of overlapping peaks. Key findings include:

• Estragole (m/z 148.11) and hexyl isothiocyanate (m/z 72.01) were resolved despite coelution and confirmed by unique extracted ion traces and spectral matching.
• Estragole appeared in both raw and processed samples; hexyl isothiocyanate was primarily elevated in the processed sample, indicating processing-induced glucosinolate breakdown.
• Peak property filters identified multiple sulfur compounds: processed samples showed various isothiocyanates, while raw samples contained sulfides such as dimethyl trisulfide and S-methyl hexanethioic acid.
• Extracted ion chromatograms of isobutyl isothiocyanate, dimethyl trisulfide, and S-methyl hexanethioic acid highlighted distinct odor-active profiles between sample types.

Benefits and Practical Applications

• Non-targeted GC-TOFMS profiling uncovers subtle processing effects on flavor compounds.
• Peak deconvolution and property filters streamline detection of sample-distinguishing analytes.
• Applications include quality control, product differentiation, and flavor optimization in the food industry.

Future Trends and Opportunities

Advancements may include integration of high-resolution mass spectrometry with machine learning for automated compound annotation, expansion of deconvolution algorithms to complex matrices, and development of real-time monitoring platforms for industrial processing.

Conclusion

GC-TOFMS with advanced deconvolution and peak filtering effectively differentiates raw versus processed broccoli by pinpointing sulfur volatiles that govern sensory properties. The approach offers deeper insights into processing-induced chemical transformations than conventional methods.

References

No external references were cited in the original text.